Can the potato really help to fight obesity?

April 2015
L-R: Professors Danielle Donnelly, Stan Kubow and Luis Agellon

L-R: Professors Danielle Donnelly, Stan Kubow and Luis Agellon

Three researchers at McGill University think so…

It all began with a chance meeting at the airport between colleagues Danielle Donnelly, a potato expert in the Department of Plant Science, and Stan Kubow of the School of Dietetics and Human Nutrition, an expert on the impact of nutritional interventions on human health.

Donnelly had been using in vitro techniques for the genetic improvement of processing cultivars of potato screening for yield and good frying quality after long-term storage. Kubow suggested that they collaborate and screen for nutritional properties as well, in particular polyphenols, powerful antioxidants with known health benefits that may contribute to the prevention of high blood pressure, heart disease, diabetes, and even tumor growth.

The potato is grown in eighty percent of countries worldwide and is eaten more often than all other vegetables combined. It ranks fourth in economic importance after rice, wheat and corn, and delivers two to three times more nutritional value per serving than any of these crops. Potatoes have the advantage of being inexpensive to produce and account for over thirty percent of all vegetable farm cash receipts in Canada.

Testing the potato

Much of Donnelly’s research has centred on the potato variety Russet Burbank, the preferred potato of most North American processors. She has selected and tested over 800 somaclonal variants—variants produced via tissue culture. Her top 25 lines for yield and processing attributes were reduced to four variants containing higher levels of polyphenols—from two to four times higher—than in the traditional Russet Burbank.

Donnelly and Kubow wanted to know the extent to which the potato polyphenols affect health, and the quantity of potatoes that would need to be consumed to have an effect. It was at this juncture that Luis Agellon, an expert in the area of Nutrigenomics (and also of the School of Dietetics and Human Nutrition), jumped on board to help them delve into this area of research.

In a study that spanned a period of 2 years, lab mice were fed an obesity- and diabetes-inducing diet over a 10-week period. One test group was supplemented with a concentrated mixture of polyphenols extracted from potatoes, equivalent to eating thirty potatoes per day for a human, and another group with the equivalent in one or a combination of two commercially produced polyphenols. The results were unexpected—although all test groups put on weight, those fed the polyphenol-rich potato extract gained significantly less weight, were generally more physically active, and had better blood glucose control.

“We were surprised by the results,” Luis Agellon said in a statement. “We thought ‘This can’t be right’ – in fact, we ran the experiment again using a different batch of extract prepared from potatoes grown in another season, just to be certain.”

The results were the same—mice fed the fatty diet supplemented with potato extract containing a mixture of polyphenols still did significantly better, even over those receiving only one or two types of polyphenols.

“There is something synergistic at play in the potato extract that makes it more effective,” said Kubow. “We will need to see if there is anything else in the extract that could explain its effectiveness.”

The study suggests that the addition of polyphenol-rich potato extract may be useful in controlling weight gain and improving control of blood sugar levels. The next step will be to run clinical trials, and to investigate what other health conditions can benefit from polyphenol-rich potato supplements.

 

 

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